Vancouver displaced Sydney as the least-affordable housing market after Hong Kong among large English-speaking cities, as home prices rose faster than incomes, a study of 325 metropolitan areas worldwide showed.

Vancouver’s median home price of C$678,000 ($686,400) in the third quarter was 10.6 times its median pretax household income of C$63,800, making the city “severely unaffordable,” Demographia said in a report today. A ratio of 3 or less is considered “affordable,” according to the public-policy firm’s survey of markets in Australia, New Zealand, Ireland, the U.K., the U.S., Canada and Hong Kong.

Sydney’s ratio of median home price to income was 9.2, while Hong Kong’s was 12.6, a record for the eight-year-old survey, surpassing the previous high of 11.5 for Los Angeles in 2007. Home prices in Hong Kong, Vancouver and Sydney haven’t plunged as they have elsewhere, such as in Ireland, now the second most-affordable country, after the U.S., the study said.

“Housing affordability generally improved in the surveyed nations, though the most unaffordable markets, Hong Kong and Vancouver, became even more unaffordable,” wrote Wendell Cox, principal of Belleville, Illinois-based Demographia, and Hugh Pavletich, managing director of Pavletich Properties Ltd., a commercial developer and investment company in Christchurch, New Zealand.

Policies limiting lots available for construction drove up land prices, putting homes out of reach for middle-class buyers and younger workers in cities such as Vancouver and Sydney, the researchers said. The median price of a detached house in metropolitan Vancouver reached a record C$900,000 in April 2011, according to the Real Estate Board of Greater Vancouver.

Massively Deteriorating’

“The causes of massively deteriorating housing affordability are not a mystery,” Cox and Pavletich said. “They inevitably result from more restrictive land-use regulations adopted by governments with insufficient attention to economic fundamentals.”